Silicon-based quantum computing

Silicon-based quantum computing related imageQuantum computers promise to solve some of the most computationally challenging tasks in strategic sectors as diverse as Healthcare, Pharma, Chemicals, Finance, Energy and Defense. To achieve deliver a quantum computer, quantum hardware needs to be developed and scaled up while managing the unavoidable errors that occur during computation. 

Several hardware platforms have been proposed. Technologies such as ion traps or superconducting qubits are leading the first wave of development with machines of a few hundreds of qubits. However, current hardware approaches to ion-trap and superconducting qubits offer limited prospects for scalability with qubit densities of the order of 1 and 100 qubits/cm2, respectively. Building a fault-tolerant quantum computer for advanced algorithms with those technologies will translate into machines of the size of a room or even a football stadium, and hence a sizable infrastructure investment comparable to that of large-scale scientific facilities.

Our team focuses on an alternative technology: spins in silicon. We leverage the very same hardware that is used in standard electronics and forms part of microprocessors, memory devices and telecommunication circuits, i.e. the silicon transistor. Building qubits based on the spin degree of freedom of individual electrons in silicon nanodevices offers numerous advantages over competing technologies: The scalability of the most compact solid-state approach, with typical qubit footprint in the range of 100 x 100 nm2, and the extensive industrial infrastructure of silicon transistor technology devoted to fabricating multi-billion-element integrated circuits. Besides, silicon electron spin qubits are one of the most coherent systems in nature, a characteristic that has enabled demonstrating all the operational steps – initialization, control and readout – with sufficient level of precision for fault-tolerant computing. In fact, silicon qubits are one of the most complete solid-state qubit implementations in terms of overall qubit fidelity, showing control fidelity above 99.5% and readout fidelity above 99.9%, all well above the threshold for quantum error correction. 

Our team has contributed to achieve some major milestones in the field:

Quantum operations on silicon spin qubits:

  • Exchange control in a MOS double quantum dot made using a 300 mm wafer process, arxiv

  • Fast high-fidelity single-shot readout of spins in silicon using a single-electron box, Phys Rev X

Integration of quantum and classical electronics:

  • A cryo-CMOS chip that integrates silicon quantum dots and multiplexed dispersive readout electronics, Nature Electronics

  • A CMOS dynamic random access architecture for radio-frequency readout of quantum devices, Nature Electronics 

  • Rapid cryogenic characterisation of 1024 integrated silicon quantum dots, arxiv

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